If I was planning to make a one-play-time game, yes I'd not bother to not even make a installer for it, the project I'm working on atm is supposed to have at least 10hr of gameplay, that's why I think the user would be plased not have to relocate his save files everytime there's a new version of the game. That was one of the critiques about itch.io, I got from people is steam: it's hard to manage updates.
I myself am not a fan of installers either, so I understand an auto-update could trigger some disconfort in some people, thanks to your input, I will prompt a message asking if the user wants the game update itself once a new version is out there, if not I'll simply prompt a link to the download page.